i'm from egypt, summer here is literally hell, in average its 38c day time, sometimes its higher, lowest is 34-35c
I won't deny Egypt is hotter than Aus. during summer. But my point still stands 75c is fine for a gpu. Technically 80c is fine. I think you're supposed to start getting worried when it hits 90c. And since you wont be overclocking you will be fine.
I'd go for the msi one over the g1. I'm positive it's a better performing card and the utility software is way better. I use msi afterburner with my g1 instead of the gigabyte one. Easy to monitor temps and lower voltages if you start feeling worried.